1. Field of the Invention
This invention relates to an improved cylinder bed type overlock sewing machine and, more particularly, to a needle plate structure for such a sewing machine, which is capable of so moving a throat plate transversely and longitudinally as to locate the optimum needle penetrating point.
2. Description of the Related Art
In general, flat bed type sewing machines as disclosed in U.S. Pat. No. 3,145,672 and cylinder bed type machines, as illustrated in FIG. 1, which are adapted to locate or direct the needle on or to a cylinder bracket 2 extending from one side of the sewing machine body, have been well known in the field of overlock sewing machines.
Sewing machines of this class have parts and elements arranged, assembled and adjusted so as to locate the needle N, if actuated, on a reference needle penetrating point C of a needle plate 1.
Practically speaking, the point of the needle N is, however, caused to be out of alignment with the reference needle penetrating point C when operated and in some cases the needle impinges against the needle plate 1 due to dimensional tolerances of the parts of the sewing machine and poor assembly of the machine parts. This causes poor sewn product and causes breakage in the needle. In this instance, the conventional approach has been to disassemble the sewing machine, exchange certain parts and re-adjust the position of the needle plate, thus leading to lower reliability of the sewing machine and lower sewing efficiency.